At the present time, techniques of removing excess hair are no longer applicable solely to women with problems of hirsutism or hypertrichosis, but are commonly practiced on patients of both sexes, who are not necessarily suffering from specific diseases, but may require treatment for purely cosmetic purposes. The procedures commonly used for this purpose can be classified according to the duration of the results. According to this classification, there are short-term systems (razors, tweezers, cold and hot waxing, creams, gels and electrical depilators), and long-term systems which, after a certain number of sessions, can even yield permanent results. Some examples of this second group of systems are electrocoagulation needles, radio frequency scalpel needles, non-coherent light and lasers. Among the long-term treatment methods, the greatest success has been obtained with the use of systems based on the theory of selective photothermolysis, which cause damage to the hair bulb by means of the electromagnetic energy absorbed by the melanin present in the hair or by the hemoglobin of the follicle blood vessels.
Non-coherent light and laser depilation systems are more effective when they strike the hair in the growth phase (“anagen”). The growth of hair is not continuous, but cyclical: a rest period called “telogen” follows each growth period called “anagen”; the transition period between the two phases is known as “catagen”. The duration of the cycle is different in the different regions, varying from 2–6 years for the head hair to only 4–8 weeks for the eyebrows. According to current biological models, the cells giving rise to the follicle are located in what is known as the “bulge area”. These cells form the new hair matrix, thus initiating the growth phase. In the initial part of this phase, when the follicle is shorter, the papilla is closer to the skin surface; subsequently it increases its length, proliferating for a period which varies according to the anatomical location. It is in the initial phase of anagen, or anagen 1, that the “target” structures of the follicle (such as the papilla and the bulge area) with its vascular system are closer to the hair and to the skin surface; as the papilla and the end part of the hair become closer, there is a greater probability that the “light” energy absorbed by the melanin of the skin, and that which arrives directly, will cause irreparable damage to the papilla, permanently blocking its ability to make a hair grow. From what has been stated above, it is evident why the action of a “photodepilation” system is more effective in the anagen phase.
In a non-coherent light depilation system, use is made of a discharge lamp, normally consisting of a cylindrical container of material which is transparent to the electromagnetic radiation in the visible band and in the near infrared. Inside the container, at a suitable pressure, there is a pure gas or a mixture of gases, according to the characteristics to be obtained for the emitted light spectrum. At the ends of the container there are two electrodes, positioned in glass-metal seals so that one end of each electrode faces the internal environment, where the desired gaseous atmosphere has been created, while the other end forms an externally accessible current lead for the electrical power supply. The structure of the discharge lamp is typically rectilinear. When the lamp is excited by suitable levels of voltage and current, according to time-based control laws, a discharge is initiated in the mixture contained in it, generating the emission of the radiation. The lamp has to be very close to the skin, or more generally close to the surface to be treated, in order to obtain the maximum intensity. To maximize the effectiveness of the treatment, the handpiece must not mask any part of the surface to be treated with portions, such as the electrodes and current leads, which are not active because they do not emit radiation. A good illustration of this point is provided by the depilatory application. In this case, the irradiation of the skin must be carried out in a uniform way, in order to avoid having untreated areas or areas in which treatment is repeated, especially in adjacent areas affected by two successive treatments. In other words, the operator must take great care when maneuvering the application unit containing the lamp, in order to provide continuity of treatment in the areas adjacent to the area concerned. It is therefore very important for the operator to have a full view of the portion of skin or other surface concerned on which the radiation is to be made to act, wherever the application unit is positioned.
The conventional structure of the lamps described above does not allow the irradiated portion to be viewed satisfactorily, since the application handpiece has two inactive areas, namely the parts occupied by the electrodes and by the current leads, where there is no discharge and consequently no emission of radiation.
To overcome this problem of masking by inactive parts, application handpieces have been developed with conventional lamps, in which optical guide structures are placed in the emitting region of the lamp to guide the light towards the surface to be treated, thus enabling the light source to be moved away from said surface. However, these handpieces are of complicated design, and do not fully overcome the aforementioned problems.